With more than 800 members, G-protein-coupled receptors (GPCRs) represent the largest family of cell surface molecules involved in signal transmission, accounting for >2% of the total genes encoded by human genome. Members of the GPCR superfamily share a common membrane topology: an extracellular N-terminus, an intracellular C-terminus and seven transmembrane (TM) helices, which are connected by three intracellular loops and three extracellular loops. On the basis of their shared topological structure, GPCRs are also referred to as seven transmembrane (7TM) receptors. These receptors control key physiological functions, including neurotransmission, hormone and enzyme release from endocrine and exocrine glands, immune responses, cardiac- and smooth-muscle contraction and blood pressure regulation. Their dysfunction contributes to some of the most prevalent human diseases. Emerging experimental and clinical data indicate that GPCRs have a crucial role in cancer progression and metastasis. Hence, there is the possibility that some GPCRs may be suitable targets for anti-cancer drugs.
Chemokines play an important role inter alia in immune and inflammatory responses in various diseases and disorders, including cancer, viral infections, asthma and allergic diseases, as well as autoimmune pathologies such as rheumatoid arthritis and atherosclerosis. These small, secreted molecules are a growing superfamily of 8-14 kDa proteins characterised by a conserved four cysteine motif.
Studies have demonstrated that the actions of chemokines are mediated by subfamilies of G protein-coupled receptors, among which is the receptor designated chemokine (C—C motif) receptor 4, or CC chemokine receptor 4 (CCR4). Specific ligands for CCR4 include the chemokines thymus and activation-regulated chemokine (TARC) (also known as CCL17) and macrophage-derived chemokine (MDC) (also known as CCL22). CCR4 may also bind to RANTES, MCP-1 and MIP-1alpha, and CCR4 signalling in response to these ligands has also been reported.
CCR4 is believed to be important inter alia in the function of T cell chemotaxis and the migration of phagocytic cells to sites of inflammation. CCR4 is preferentially expressed on T-helper cell type 2 (Th2) cells and regulatory T (Treg) cells, whereas only limited expression on other healthy cells or tissues occurs.
Tumour cells, in particular adult T cell leukaemia/lymphoma cells, may be positive for CCR4. Expression of CCR4 by tumour cells is associated with skin involvement. Certain T-cell malignancies typically are located to the skin. For example, CCR4 is found at high levels in cutaneous T cell lymphoma lesions.
More recently, CCR4 has also been found to be expressed by certain solid tumours (WO2009/037454). CCR4 expression is believed to be an early event in carcinogenesis of solid tumours, particularly cancer of the cervix, oesophagus, kidney, brain, breast, ovary, prostate, stomach and pancreas. Thus, both haematological and non-haematological cancer cells may express CCR4. Consequently, these cancers may be diagnosed, monitored and treated using anti-CCR4 antibodies.
In addition, CCR4 has an important role in normal and tumour immunity. A significant fraction of CD4+CD25+ regulatory T-cells (Tregs) are positive for CCR4 (Baatar et al, 2007b). These Tregs suppress immune responses through a variety of mechanisms, and it has been shown that they can inhibit tumour-specific immunity. Increased numbers of Tregs infiltrating the stroma, the tumour itself, or draining lymphnodes, correlate with worsened outcome in a variety of cancers. Studies in mouse model show that reducing Treg activity leads to increased endogenous anti-tumour immunity and increased efficacy of anti-tumour interventions by the immune system. Consequently, inhibiting Treg function is a promising strategy in immunotherapy of tumours. The inhibition can be achieved by killing the Tregs (depletion), interfering with their suppressor functions, changing their trafficking pattern or changing their differentiation.
In a subset of patients with CCR4+ T-cell leukaemia/lymphoma, the tumour cells themselves function as Treg cells, contributing to tumour survival in the face of host antitumour immune responses. In other types of cancers, MDC and TARC are produced by tumour cells and the tumour microenvironment and attract CCR4+ Treg cells to the tumour, where they create a favourable environment for tumour escape from the host immune responses. A higher frequency of Tregs in peripheral blood of patients with following cancers has been reported: Breast cancer, Colorectal cancer, Oesophageal cancer, Gastric cancer, Hepatocellular carcinoma, Lung cancer, Melanoma, Ovarian cancer and Pancreatic cancer. Treg cells have been reported to create a favourable environment for tumours. Hence, blocking the interaction between CCR4 and its ligands such as MDC could be useful in the treatment or prevention of cancers, especially the cancers listed above. It has been reported that in a SCID mouse model, antibody to human MDC/CCL22 was able to block infiltration of human Treg cells into transplanted human ovarian tumours. It is believed that the Treg cells present in human solid tumours prevent immune effector responses developing which could contribute to the slowing of tumour growth and metastasis. Thus, killing of Treg cells in the tumour mass, and/or prevention of migration of Treg cells to the tumour sites by using a neutralising MAb (monoclonal antibody) directed against CCR4 may result in enhanced immune responses towards solid tumours, and act as an adjunct to conventional cytotoxic or anti-hormonal therapies.
Cancer causes about 13% of all human deaths. According to the American Cancer Society, 7.6 million people died from cancer in the world during 2007, so there remains a strong and urgent need for further anti-cancer therapeutics.
CCR4 has been shown to play a role in inflammation and immune disorders. Th2 cells and basophils are key cells in the allergic response in the lung and skin. There are a number of reports which describe the presence of CCR4-expressing T cells and concomitant expression of CCR4 ligands (MDC, TARC) on airway epithelial cells in bronchial biopsies in allergen-challenged asthmatics (Panina-Bordignon et al, 2001). CCR4+ T cells are also found in increased numbers in patients with atopic dermatitis, with a marked reduction of CCR4+ T cells observed when the disease improved. Using a humanized SCID mouse model of asthma, it was shown that blockade of CCR4 with antibodies prior to allergen challenge reduced allergic airway inflammation, as well as the levels of Th2 cytokines in the lungs. Depletion of CCR4+ T cells via lung delivery of a blocking antibody may be a suitable treatment option for asthmatic patients. Targeted delivery of a CCR4 blocking antibody to the skin may also be an attractive treatment for atopic dermatitis.
In allergic asthma, the presence of high levels of allergen-specific IgE is a reflection of an aberrant Th2 cell immune response to commonly inhaled environmental allergens. Asthma is characterized by infiltration of Th2 lymphocytes and eosinophils and by the production of Th2 chemokines. Allergens are presented to T cells by dendritic cells (DCs) that continuously sample incoming foreign antigens. Upon proper activation by DCs, allergen-specific lymphocytes that are present in diseased airways produce Th2 cytokines interleukin (IL)-4, IL-5 and IL-13 that furthermore control leukocyte extravasation, goblet cell hyperplasia and bronchial hyper-reactivity (BHR). TARC and MDC produced by DCs induce the selective migration of Th2 cells but not Th1 cells through triggering CCR4 (Perros et al, 2009). It was shown in murine models of asthma, that treatment with anti-TARC antibodies reduced the number of CD4+ T cells and eosinophils in bronchoalveolar lavage (BAL) fluid, the production of Th2 cytokines and airway hyper-responsiveness after allergen challenge (Kawasaki et al, 2001). In contrast, CCR4-deficient mice showed no protection against airway inflammation and BHR (Chvatchko et al, 2000). Using a humanized SCID mouse model of asthma, it was shown that blockade of CCR4 with antibodies prior to allergen challenge reduced allergic airway inflammation as well as the levels of Th2 cytokines in the lungs (Perros et al, 2009). These data indicate that CCR4 blockade is a feasible strategy for inhibiting allergic inflammation in humans.
Treg cells may suppress dendritic cells (DCs), thereby facilitating the development and progression of diseases, particularly infectious diseases and cancer. Anti-CCR4 antibodies able to block the suppression of dendritic cells by Treg cells may therefore be useful as adjuvants in vaccines, particularly as adjuvants in tumour vaccination or vaccination against infectious disease. Thus, an anti-CCR4 antibody may enhance the therapeutic effect of a vaccine, particularly enhancing the vaccine-induced immune response.
CCR4 binding compounds have been reported to show efficacy in murine allergic inflammation (Purandare et al, 2007, Burdi et al. 2007). It has been reported that a CCR4-binding compound has reasonable potency in vivo, as CCR4 dependent recruitment of leucocytes to the peritoneum induced by TARC was inhibited by almost 90%. Yokoyama and colleagues presented a quinazoline derivative targeting CCR4 which proved in vivo to be effective in reducing hypersensitivity reactions in a mouse model (Yokoyama et al, 2008b); a derivative of this compound proved to be effective in a similar in vivo mouse model upon oral administration (Yokoyama et al, 2009). Recently, a group of scientists has identified a number CCR4 antagonists using in silico modelling approach (Bayry et al, 2008; Davies et al, 2009). By docking compounds to modelled CCR4, the authors found molecules able to bind within the transmembrane region. Sixteen compounds inhibited CCR4-mediated migration of CCRF-CEM cells. When CCR4 antagonists were tested for their adjuvant function in vivo with Mycobacterium tuberculosis and hepatitis B vaccines, enhanced immunogenicity was observed for both cellular and humoral immune responses. The observed effect was ascribed to inhibition of Treg activity (Bayry et al, 2008; Davies et al, 2009). The fact that a significant fraction of Treg cells are CCR4-positive is well known in the art (Baatar et al 2007b). The observed effect is believed to be useful not only in the context of vaccination against infectious diseases (caused, for example by a virus, a bacterium, a mycobacterium or a parasite such as protozoa), but also in the context of cancer vaccines.
As the cause for the efficacy of these compounds as adjuvants is based on inhibiting Tregs by blocking CCR4 mediated signaling, it is expected that antibodies binding to CCR4 in an antagonistic manner would work the same way; the pharmacological advantages of antibodies compared to small molecule drugs are well known in the art. The anti-CCR4 antibody KW-0761 by Kyowa-Hakko is known in the art. However, this antibody is effective only by ADCC; it does not prevent ligand-mediated signalling through CCR4 receptor. Therefore, the antibodies described in this invention are expected to be clearly superior in their modulation of immune reactions via Tregs.
Another application where modulating Tregs is of clinical use is cancer treatment. Tregs can inhibit tumour-specific immunity and their increased numbers correlate with unfavourable prognosis and disease progression in some cancers. Studies in mouse models demonstrate that reducing Treg activity boosts endogenous anti-tumour immunity, and increases the efficacy of active immune interventions. Consequently, inhibiting Treg function is a strategy worth considering in human cancer immunotherapy (Curiel, 2008; Ruter et al, 2009). This inhibition can be achieved both by modulating Tregs, or by directly killing them.
Examples for this approaches are described in the art by compounds targeting other surface of Treg like CD25. Daclizumab (Zenapax®; Roche)) and basiliximab (Simulect®; Novartis) are anti-human CD25 antibodies approved for use in autoimmune diseases, transplantation and cancers including HTLV-1 induced adult T-cell lymphoma/leukaemia (Church, 2003). Denileukin diftitox (Ontak®, DAB389IL-2; Ligand Pharmaceuticals Inc.) is a recombinant protein fusing the active domain of diphtheria toxin to human IL-2. In 1998, FDA has approved it to treat cutaneous T cell leukaemia/lymphoma (Olsen et al, 2001), which usually are CD4+CD25+. Denileukin diftitox is targeted to the IL-2 receptor and is proposed to be internalized through CD25 by endocytosis. There is also evidence that Denileukin diftitox improves immunogenicity of a tumour vaccine in patients with renal cell cancer (Dannull et al, 2005). In addition, a report showed that denileukin diftitox reduces Treg numbers and function in melanoma with improved melanoma-specific immunity (Mahnke et al, 2007)
Other molecules on Tregs which are targeted for cancer treatment or improved cancer vaccine effects include GITR (glucocorticoid-induced tumour necrosis factor receptor-related gene) (Levings et al, 2002), Toll-like receptors (TLR) are expressed ubiquitously on a variety of mammalian cells, including human Tregs (Yang et al, 2004, Rutter et al, 2009) and Cytotoxic T lymphocyte antigen-4 (CTLA-4; CD152) (Sutmuller et al. 2001). Currently, Phase II and III clinical trials of anti-CTLA-4 monoclonal antibody therapy are being conducted in melanoma, and Phase I and II trials are being conducted in other tumour types. Two human monoclonal antibodies are under investigation—ipilimumab (MDX-010; Bristol-Myers Squibb/Medarex) and tremelimumab (CP-675,206; Pfizer).
CCR4 has also been implicated inter alia in the following disorders: Adult T-cell leukemia/lymphoma, Peripheral T-cell lymphoma, Cutaneous T-Cell Lymphoma (CTCL), unspecified Diffuse large B-cell lymphoma, Hodgkin's lymphoma, B-cell chronic lymphocytic leukemia, Epstein-Barr virus (EBV) infection, Mycosis fungoides (a mature T-cell lymphoma), Sezary syndrome (a variant of mycosis fungoides), allergic bronchopulmonary aspergillosis (ABPA), Asthma, LPS-induced endotoxic shock, Allergic inflammation, T-cell mediated neurodegenerative diseases such as Multiple Sclerosis (MS), Autoimmune diseases such as Psoriasis, Castleman's disease and Rheumatoid arthritis (RA).
Due to their complex structures, GPCRs are considered as “difficult targets” for raising specific antibodies. They can neither be easily purified from the membrane fraction of lysed cells, nor be recombinantly produced in different expression systems as correctly folded soluble proteins. To the inventors' knowledge, to date all known attempts of others to generate anti-GPCR antibodies using phage display have proven to be unsuccessful.
The difficulties associated with generating antibodies against GPCRs are set out in Hoogenboom et al., 1999. Furthermore, Sui et al. (2003) explain the difficulties associated with trying to obtain human antibodies against the GPCR chemokine receptor CXCR4 and report that even using the pathfinder method combined with step-back selection no specific antibodies could be identified. Thus, in the field of GPCRs, the generation of specific antibodies remains a major challenge.
A murine monoclonal antibody called 1G1 which reacts with human CCR4 is commercially available from BD Pharmingen. This antibody may be used for immunoflurescent staining, but the antibody is not a neutralising antibody.
A chimeric antibody to CCR4 designated KM2760 is disclosed in Ishida et al., 2006. The authors report that this antibody does not block the binding of CCR4 to its ligands MDC or TARC.
The inventors have recognized that the identification of additional antibodies that recognize CCR4 would be of benefit in expanding the number of therapeutic options. In particular, antibodies that block the binding of CCR4 to one or more of its ligands would offer further therapeutic avenues.
The inventors have also recognized that the development of therapeutic agents for the treatment of humans that are better tolerated from an immunological perspective would be advantageous. In this regard, human antibodies generally have at least three potential advantages for use in human therapy. First, the human immune system should not recognize the antibody as foreign. Second, the half-life in the human circulation will be similar to naturally occurring human antibodies, allowing smaller and less frequent doses to be given. Third, because the effector portion is human, it will interact better with the other parts of the human immune system.
The art therefore still lacks anti-CCR4 antibodies that can be used in the safe and effective treatment of patients having disorders in which CCR4 is involved, including in long-term administration, and poses challenges to the development of such antibodies.
In particular, there is a need for human antibodies to CCR4. Although human antibodies are generally recognized to display advantages, it is known that the development of human antibodies that have high enough affinities and appropriate functional properties to make them candidates for successful human therapy is by no means straightforward. This is even more so the case with GPCRs, due to their complex and transmembrane nature.
There also remains a strong need for anti-CCR4 antibodies which can block the binding between CCR4 and one or more of its ligands such as MDC and/or TARC.